1. Field of the Invention
The invention relates to a method of manufacturing jet nozzle ducts, notably for ink jet printers, in which an approximately radially polarized tubular piezo-electric pumping member is arranged around a portion of each jet nozzle duct to be formed in order to obtain a pumping section. The invention also relates to an ink jet printer comprising a printing head with at least one jet nozzle duct manufactured by means of the method.
2. Description of the Prior Art
From U.S. Pat. No. 3,832,579 an ink jet printer is known which comprises a jet nozzle duct which consists partly of a cylindrical glass tube around which a pumping member is secured by means of an adhesive in order to form a pumping section. The pumping member consists of a tube of radially polarized piezo-electric ceramic material, for example lead zirconate titanate (PXE) whose internal and external surfaces are provided with metal electrodes. When an electric voltage is applied to the pumping member via the electrodes, mechanical deformation occurs. As a result, the diameter of the pumping member is slightly reduced, so that the glass tube is also slightly compressed. Consequently, a pressure wave is produced in a liquid (ink) with which the glass tube is filled, so that a droplet of liquid is ejected via a nozzle at one end of the tube. The other end of the tube is connected to an ink reservoir. This connection comprises a constriction or a portion having a wall of an energy-absorbing material in order to prevent propagation of the pressure wave in the direction of the reservoir. Jet nozzle ducts of this kind can be used not only in ink jet printers, but also in other devices, such as liquid atomizers, for example, for medical applications.
It has been found in practice that it is difficult to manufacture piezo-electric tubes for pumping members with adequate precision. The customarily used extrusion processes offer tubes having dimensions and piezo-electric properties which are not very well reproducible. Moreover, the provision of an electrode on the internal surface is difficult from a technical point of view and is also expensive.